2 * Copyright (c) 1991 Regents of the University of California.
4 * Copyright (c) 1994 John S. Dyson
6 * Copyright (c) 1994 David Greenman
9 * This code is derived from software contributed to Berkeley by
10 * The Mach Operating System project at Carnegie-Mellon University.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * from: @(#)vm_pageout.c 7.4 (Berkeley) 5/7/91
43 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
44 * All rights reserved.
46 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
48 * Permission to use, copy, modify and distribute this software and
49 * its documentation is hereby granted, provided that both the copyright
50 * notice and this permission notice appear in all copies of the
51 * software, derivative works or modified versions, and any portions
52 * thereof, and that both notices appear in supporting documentation.
54 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
55 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
56 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
58 * Carnegie Mellon requests users of this software to return to
60 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
61 * School of Computer Science
62 * Carnegie Mellon University
63 * Pittsburgh PA 15213-3890
65 * any improvements or extensions that they make and grant Carnegie the
66 * rights to redistribute these changes.
68 * $FreeBSD: src/sys/vm/vm_pageout.c,v 1.151.2.15 2002/12/29 18:21:04 dillon Exp $
69 * $DragonFly: src/sys/vm/vm_pageout.c,v 1.24 2006/08/12 00:26:22 dillon Exp $
73 * The proverbial page-out daemon.
77 #include <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
81 #include <sys/kthread.h>
82 #include <sys/resourcevar.h>
83 #include <sys/signalvar.h>
84 #include <sys/vnode.h>
85 #include <sys/vmmeter.h>
86 #include <sys/sysctl.h>
89 #include <vm/vm_param.h>
91 #include <vm/vm_object.h>
92 #include <vm/vm_page.h>
93 #include <vm/vm_map.h>
94 #include <vm/vm_pageout.h>
95 #include <vm/vm_pager.h>
96 #include <vm/swap_pager.h>
97 #include <vm/vm_extern.h>
99 #include <sys/thread2.h>
100 #include <vm/vm_page2.h>
103 * System initialization
106 /* the kernel process "vm_pageout"*/
107 static void vm_pageout (void);
108 static int vm_pageout_clean (vm_page_t
);
109 static void vm_pageout_scan (int pass
);
110 static int vm_pageout_free_page_calc (vm_size_t count
);
111 struct thread
*pagethread
;
113 static struct kproc_desc page_kp
= {
118 SYSINIT(pagedaemon
, SI_SUB_KTHREAD_PAGE
, SI_ORDER_FIRST
, kproc_start
, &page_kp
)
120 #if !defined(NO_SWAPPING)
121 /* the kernel process "vm_daemon"*/
122 static void vm_daemon (void);
123 static struct thread
*vmthread
;
125 static struct kproc_desc vm_kp
= {
130 SYSINIT(vmdaemon
, SI_SUB_KTHREAD_VM
, SI_ORDER_FIRST
, kproc_start
, &vm_kp
)
134 int vm_pages_needed
=0; /* Event on which pageout daemon sleeps */
135 int vm_pageout_deficit
=0; /* Estimated number of pages deficit */
136 int vm_pageout_pages_needed
=0; /* flag saying that the pageout daemon needs pages */
138 #if !defined(NO_SWAPPING)
139 static int vm_pageout_req_swapout
; /* XXX */
140 static int vm_daemon_needed
;
142 extern int vm_swap_size
;
143 static int vm_max_launder
= 32;
144 static int vm_pageout_stats_max
=0, vm_pageout_stats_interval
= 0;
145 static int vm_pageout_full_stats_interval
= 0;
146 static int vm_pageout_stats_free_max
=0, vm_pageout_algorithm
=0;
147 static int defer_swap_pageouts
=0;
148 static int disable_swap_pageouts
=0;
150 #if defined(NO_SWAPPING)
151 static int vm_swap_enabled
=0;
152 static int vm_swap_idle_enabled
=0;
154 static int vm_swap_enabled
=1;
155 static int vm_swap_idle_enabled
=0;
158 SYSCTL_INT(_vm
, VM_PAGEOUT_ALGORITHM
, pageout_algorithm
,
159 CTLFLAG_RW
, &vm_pageout_algorithm
, 0, "LRU page mgmt");
161 SYSCTL_INT(_vm
, OID_AUTO
, max_launder
,
162 CTLFLAG_RW
, &vm_max_launder
, 0, "Limit dirty flushes in pageout");
164 SYSCTL_INT(_vm
, OID_AUTO
, pageout_stats_max
,
165 CTLFLAG_RW
, &vm_pageout_stats_max
, 0, "Max pageout stats scan length");
167 SYSCTL_INT(_vm
, OID_AUTO
, pageout_full_stats_interval
,
168 CTLFLAG_RW
, &vm_pageout_full_stats_interval
, 0, "Interval for full stats scan");
170 SYSCTL_INT(_vm
, OID_AUTO
, pageout_stats_interval
,
171 CTLFLAG_RW
, &vm_pageout_stats_interval
, 0, "Interval for partial stats scan");
173 SYSCTL_INT(_vm
, OID_AUTO
, pageout_stats_free_max
,
174 CTLFLAG_RW
, &vm_pageout_stats_free_max
, 0, "Not implemented");
176 #if defined(NO_SWAPPING)
177 SYSCTL_INT(_vm
, VM_SWAPPING_ENABLED
, swap_enabled
,
178 CTLFLAG_RD
, &vm_swap_enabled
, 0, "");
179 SYSCTL_INT(_vm
, OID_AUTO
, swap_idle_enabled
,
180 CTLFLAG_RD
, &vm_swap_idle_enabled
, 0, "");
182 SYSCTL_INT(_vm
, VM_SWAPPING_ENABLED
, swap_enabled
,
183 CTLFLAG_RW
, &vm_swap_enabled
, 0, "Enable entire process swapout");
184 SYSCTL_INT(_vm
, OID_AUTO
, swap_idle_enabled
,
185 CTLFLAG_RW
, &vm_swap_idle_enabled
, 0, "Allow swapout on idle criteria");
188 SYSCTL_INT(_vm
, OID_AUTO
, defer_swapspace_pageouts
,
189 CTLFLAG_RW
, &defer_swap_pageouts
, 0, "Give preference to dirty pages in mem");
191 SYSCTL_INT(_vm
, OID_AUTO
, disable_swapspace_pageouts
,
192 CTLFLAG_RW
, &disable_swap_pageouts
, 0, "Disallow swapout of dirty pages");
194 static int pageout_lock_miss
;
195 SYSCTL_INT(_vm
, OID_AUTO
, pageout_lock_miss
,
196 CTLFLAG_RD
, &pageout_lock_miss
, 0, "vget() lock misses during pageout");
199 SYSCTL_INT(_vm
, OID_AUTO
, vm_load
,
200 CTLFLAG_RD
, &vm_load
, 0, "load on the VM system");
201 int vm_load_enable
= 1;
202 SYSCTL_INT(_vm
, OID_AUTO
, vm_load_enable
,
203 CTLFLAG_RW
, &vm_load_enable
, 0, "enable vm_load rate limiting");
206 SYSCTL_INT(_vm
, OID_AUTO
, vm_load_debug
,
207 CTLFLAG_RW
, &vm_load_debug
, 0, "debug vm_load");
210 #define VM_PAGEOUT_PAGE_COUNT 16
211 int vm_pageout_page_count
= VM_PAGEOUT_PAGE_COUNT
;
213 int vm_page_max_wired
; /* XXX max # of wired pages system-wide */
215 #if !defined(NO_SWAPPING)
216 typedef void freeer_fcn_t (vm_map_t
, vm_object_t
, vm_pindex_t
, int);
217 static void vm_pageout_map_deactivate_pages (vm_map_t
, vm_pindex_t
);
218 static freeer_fcn_t vm_pageout_object_deactivate_pages
;
219 static void vm_req_vmdaemon (void);
221 static void vm_pageout_page_stats(void);
227 vm_fault_ratecheck(void)
229 if (vm_pages_needed
) {
241 * Clean the page and remove it from the laundry. The page must not be
244 * We set the busy bit to cause potential page faults on this page to
245 * block. Note the careful timing, however, the busy bit isn't set till
246 * late and we cannot do anything that will mess with the page.
250 vm_pageout_clean(vm_page_t m
)
253 vm_page_t mc
[2*vm_pageout_page_count
];
255 int ib
, is
, page_base
;
256 vm_pindex_t pindex
= m
->pindex
;
261 * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP
262 * with the new swapper, but we could have serious problems paging
263 * out other object types if there is insufficient memory.
265 * Unfortunately, checking free memory here is far too late, so the
266 * check has been moved up a procedural level.
270 * Don't mess with the page if it's busy, held, or special
272 if ((m
->hold_count
!= 0) ||
273 ((m
->busy
!= 0) || (m
->flags
& (PG_BUSY
|PG_UNMANAGED
)))) {
277 mc
[vm_pageout_page_count
] = m
;
279 page_base
= vm_pageout_page_count
;
284 * Scan object for clusterable pages.
286 * We can cluster ONLY if: ->> the page is NOT
287 * clean, wired, busy, held, or mapped into a
288 * buffer, and one of the following:
289 * 1) The page is inactive, or a seldom used
292 * 2) we force the issue.
294 * During heavy mmap/modification loads the pageout
295 * daemon can really fragment the underlying file
296 * due to flushing pages out of order and not trying
297 * align the clusters (which leave sporatic out-of-order
298 * holes). To solve this problem we do the reverse scan
299 * first and attempt to align our cluster, then do a
300 * forward scan if room remains.
304 while (ib
&& pageout_count
< vm_pageout_page_count
) {
312 if ((p
= vm_page_lookup(object
, pindex
- ib
)) == NULL
) {
316 if (((p
->queue
- p
->pc
) == PQ_CACHE
) ||
317 (p
->flags
& (PG_BUSY
|PG_UNMANAGED
)) || p
->busy
) {
321 vm_page_test_dirty(p
);
322 if ((p
->dirty
& p
->valid
) == 0 ||
323 p
->queue
!= PQ_INACTIVE
||
324 p
->wire_count
!= 0 || /* may be held by buf cache */
325 p
->hold_count
!= 0) { /* may be undergoing I/O */
333 * alignment boundry, stop here and switch directions. Do
336 if ((pindex
- (ib
- 1)) % vm_pageout_page_count
== 0)
340 while (pageout_count
< vm_pageout_page_count
&&
341 pindex
+ is
< object
->size
) {
344 if ((p
= vm_page_lookup(object
, pindex
+ is
)) == NULL
)
346 if (((p
->queue
- p
->pc
) == PQ_CACHE
) ||
347 (p
->flags
& (PG_BUSY
|PG_UNMANAGED
)) || p
->busy
) {
350 vm_page_test_dirty(p
);
351 if ((p
->dirty
& p
->valid
) == 0 ||
352 p
->queue
!= PQ_INACTIVE
||
353 p
->wire_count
!= 0 || /* may be held by buf cache */
354 p
->hold_count
!= 0) { /* may be undergoing I/O */
357 mc
[page_base
+ pageout_count
] = p
;
363 * If we exhausted our forward scan, continue with the reverse scan
364 * when possible, even past a page boundry. This catches boundry
367 if (ib
&& pageout_count
< vm_pageout_page_count
)
371 * we allow reads during pageouts...
373 return vm_pageout_flush(&mc
[page_base
], pageout_count
, 0);
377 * vm_pageout_flush() - launder the given pages
379 * The given pages are laundered. Note that we setup for the start of
380 * I/O ( i.e. busy the page ), mark it read-only, and bump the object
381 * reference count all in here rather then in the parent. If we want
382 * the parent to do more sophisticated things we may have to change
387 vm_pageout_flush(vm_page_t
*mc
, int count
, int flags
)
390 int pageout_status
[count
];
395 * Initiate I/O. Bump the vm_page_t->busy counter and
396 * mark the pages read-only.
398 * We do not have to fixup the clean/dirty bits here... we can
399 * allow the pager to do it after the I/O completes.
402 for (i
= 0; i
< count
; i
++) {
403 KASSERT(mc
[i
]->valid
== VM_PAGE_BITS_ALL
, ("vm_pageout_flush page %p index %d/%d: partially invalid page", mc
[i
], i
, count
));
404 vm_page_io_start(mc
[i
]);
405 vm_page_protect(mc
[i
], VM_PROT_READ
);
408 object
= mc
[0]->object
;
409 vm_object_pip_add(object
, count
);
411 vm_pager_put_pages(object
, mc
, count
,
412 (flags
| ((object
== kernel_object
) ? VM_PAGER_PUT_SYNC
: 0)),
415 for (i
= 0; i
< count
; i
++) {
416 vm_page_t mt
= mc
[i
];
418 switch (pageout_status
[i
]) {
427 * Page outside of range of object. Right now we
428 * essentially lose the changes by pretending it
431 pmap_clear_modify(mt
);
437 * If page couldn't be paged out, then reactivate the
438 * page so it doesn't clog the inactive list. (We
439 * will try paging out it again later).
441 vm_page_activate(mt
);
448 * If the operation is still going, leave the page busy to
449 * block all other accesses. Also, leave the paging in
450 * progress indicator set so that we don't attempt an object
453 if (pageout_status
[i
] != VM_PAGER_PEND
) {
454 vm_object_pip_wakeup(object
);
455 vm_page_io_finish(mt
);
456 if (!vm_page_count_severe() || !vm_page_try_to_cache(mt
))
457 vm_page_protect(mt
, VM_PROT_READ
);
463 #if !defined(NO_SWAPPING)
465 * vm_pageout_object_deactivate_pages
467 * deactivate enough pages to satisfy the inactive target
468 * requirements or if vm_page_proc_limit is set, then
469 * deactivate all of the pages in the object and its
472 * The object and map must be locked.
475 vm_pageout_object_deactivate_pages(vm_map_t map
, vm_object_t object
,
476 vm_pindex_t desired
, int map_remove_only
)
482 if (object
->type
== OBJT_DEVICE
|| object
->type
== OBJT_PHYS
)
486 if (pmap_resident_count(vm_map_pmap(map
)) <= desired
)
488 if (object
->paging_in_progress
)
491 remove_mode
= map_remove_only
;
492 if (object
->shadow_count
> 1)
496 * scan the objects entire memory queue. spl protection is
497 * required to avoid an interrupt unbusy/free race against
501 rcount
= object
->resident_page_count
;
502 p
= TAILQ_FIRST(&object
->memq
);
504 while (p
&& (rcount
-- > 0)) {
506 if (pmap_resident_count(vm_map_pmap(map
)) <= desired
) {
510 next
= TAILQ_NEXT(p
, listq
);
511 mycpu
->gd_cnt
.v_pdpages
++;
512 if (p
->wire_count
!= 0 ||
513 p
->hold_count
!= 0 ||
515 (p
->flags
& (PG_BUSY
|PG_UNMANAGED
)) ||
516 !pmap_page_exists_quick(vm_map_pmap(map
), p
)) {
521 actcount
= pmap_ts_referenced(p
);
523 vm_page_flag_set(p
, PG_REFERENCED
);
524 } else if (p
->flags
& PG_REFERENCED
) {
528 if ((p
->queue
!= PQ_ACTIVE
) &&
529 (p
->flags
& PG_REFERENCED
)) {
531 p
->act_count
+= actcount
;
532 vm_page_flag_clear(p
, PG_REFERENCED
);
533 } else if (p
->queue
== PQ_ACTIVE
) {
534 if ((p
->flags
& PG_REFERENCED
) == 0) {
535 p
->act_count
-= min(p
->act_count
, ACT_DECLINE
);
536 if (!remove_mode
&& (vm_pageout_algorithm
|| (p
->act_count
== 0))) {
537 vm_page_protect(p
, VM_PROT_NONE
);
538 vm_page_deactivate(p
);
540 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
541 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
545 vm_page_flag_clear(p
, PG_REFERENCED
);
546 if (p
->act_count
< (ACT_MAX
- ACT_ADVANCE
))
547 p
->act_count
+= ACT_ADVANCE
;
548 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
549 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, p
, pageq
);
551 } else if (p
->queue
== PQ_INACTIVE
) {
552 vm_page_protect(p
, VM_PROT_NONE
);
557 object
= object
->backing_object
;
562 * deactivate some number of pages in a map, try to do it fairly, but
563 * that is really hard to do.
566 vm_pageout_map_deactivate_pages(vm_map_t map
, vm_pindex_t desired
)
569 vm_object_t obj
, bigobj
;
572 if (lockmgr(&map
->lock
, LK_EXCLUSIVE
| LK_NOWAIT
)) {
580 * first, search out the biggest object, and try to free pages from
583 tmpe
= map
->header
.next
;
584 while (tmpe
!= &map
->header
) {
585 if ((tmpe
->eflags
& MAP_ENTRY_IS_SUB_MAP
) == 0) {
586 obj
= tmpe
->object
.vm_object
;
587 if ((obj
!= NULL
) && (obj
->shadow_count
<= 1) &&
589 (bigobj
->resident_page_count
< obj
->resident_page_count
))) {
593 if (tmpe
->wired_count
> 0)
594 nothingwired
= FALSE
;
599 vm_pageout_object_deactivate_pages(map
, bigobj
, desired
, 0);
602 * Next, hunt around for other pages to deactivate. We actually
603 * do this search sort of wrong -- .text first is not the best idea.
605 tmpe
= map
->header
.next
;
606 while (tmpe
!= &map
->header
) {
607 if (pmap_resident_count(vm_map_pmap(map
)) <= desired
)
609 if ((tmpe
->eflags
& MAP_ENTRY_IS_SUB_MAP
) == 0) {
610 obj
= tmpe
->object
.vm_object
;
612 vm_pageout_object_deactivate_pages(map
, obj
, desired
, 0);
618 * Remove all mappings if a process is swapped out, this will free page
621 if (desired
== 0 && nothingwired
)
622 pmap_remove(vm_map_pmap(map
),
623 VM_MIN_ADDRESS
, VM_MAXUSER_ADDRESS
);
629 * Don't try to be fancy - being fancy can lead to vnode deadlocks. We
630 * only do it for OBJT_DEFAULT and OBJT_SWAP objects which we know can
631 * be trivially freed.
634 vm_pageout_page_free(vm_page_t m
) {
635 vm_object_t object
= m
->object
;
636 int type
= object
->type
;
638 if (type
== OBJT_SWAP
|| type
== OBJT_DEFAULT
)
639 vm_object_reference(object
);
641 vm_page_protect(m
, VM_PROT_NONE
);
643 if (type
== OBJT_SWAP
|| type
== OBJT_DEFAULT
)
644 vm_object_deallocate(object
);
648 * vm_pageout_scan does the dirty work for the pageout daemon.
651 struct vm_pageout_scan_info
{
652 struct proc
*bigproc
;
656 static int vm_pageout_scan_callback(struct proc
*p
, void *data
);
659 vm_pageout_scan(int pass
)
661 struct vm_pageout_scan_info info
;
663 struct vm_page marker
;
664 int page_shortage
, maxscan
, pcount
;
665 int addl_page_shortage
, addl_page_shortage_init
;
668 int vnodes_skipped
= 0;
672 * Do whatever cleanup that the pmap code can.
676 addl_page_shortage_init
= vm_pageout_deficit
;
677 vm_pageout_deficit
= 0;
680 * Calculate the number of pages we want to either free or move
683 page_shortage
= vm_paging_target() + addl_page_shortage_init
;
686 * Initialize our marker
688 bzero(&marker
, sizeof(marker
));
689 marker
.flags
= PG_BUSY
| PG_FICTITIOUS
| PG_MARKER
;
690 marker
.queue
= PQ_INACTIVE
;
691 marker
.wire_count
= 1;
694 * Start scanning the inactive queue for pages we can move to the
695 * cache or free. The scan will stop when the target is reached or
696 * we have scanned the entire inactive queue. Note that m->act_count
697 * is not used to form decisions for the inactive queue, only for the
700 * maxlaunder limits the number of dirty pages we flush per scan.
701 * For most systems a smaller value (16 or 32) is more robust under
702 * extreme memory and disk pressure because any unnecessary writes
703 * to disk can result in extreme performance degredation. However,
704 * systems with excessive dirty pages (especially when MAP_NOSYNC is
705 * used) will die horribly with limited laundering. If the pageout
706 * daemon cannot clean enough pages in the first pass, we let it go
707 * all out in succeeding passes.
709 if ((maxlaunder
= vm_max_launder
) <= 1)
715 * We will generally be in a critical section throughout the
716 * scan, but we can release it temporarily when we are sitting on a
717 * non-busy page without fear. this is required to prevent an
718 * interrupt from unbusying or freeing a page prior to our busy
719 * check, leaving us on the wrong queue or checking the wrong
724 addl_page_shortage
= addl_page_shortage_init
;
725 maxscan
= vmstats
.v_inactive_count
;
726 for (m
= TAILQ_FIRST(&vm_page_queues
[PQ_INACTIVE
].pl
);
727 m
!= NULL
&& maxscan
-- > 0 && page_shortage
> 0;
730 mycpu
->gd_cnt
.v_pdpages
++;
733 * Give interrupts a chance
739 * It's easier for some of the conditions below to just loop
740 * and catch queue changes here rather then check everywhere
743 if (m
->queue
!= PQ_INACTIVE
)
745 next
= TAILQ_NEXT(m
, pageq
);
750 if (m
->flags
& PG_MARKER
)
754 * A held page may be undergoing I/O, so skip it.
757 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
758 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
759 addl_page_shortage
++;
764 * Dont mess with busy pages, keep in the front of the
765 * queue, most likely are being paged out.
767 if (m
->busy
|| (m
->flags
& PG_BUSY
)) {
768 addl_page_shortage
++;
772 if (m
->object
->ref_count
== 0) {
774 * If the object is not being used, we ignore previous
777 vm_page_flag_clear(m
, PG_REFERENCED
);
778 pmap_clear_reference(m
);
780 } else if (((m
->flags
& PG_REFERENCED
) == 0) &&
781 (actcount
= pmap_ts_referenced(m
))) {
783 * Otherwise, if the page has been referenced while
784 * in the inactive queue, we bump the "activation
785 * count" upwards, making it less likely that the
786 * page will be added back to the inactive queue
787 * prematurely again. Here we check the page tables
788 * (or emulated bits, if any), given the upper level
789 * VM system not knowing anything about existing
793 m
->act_count
+= (actcount
+ ACT_ADVANCE
);
798 * If the upper level VM system knows about any page
799 * references, we activate the page. We also set the
800 * "activation count" higher than normal so that we will less
801 * likely place pages back onto the inactive queue again.
803 if ((m
->flags
& PG_REFERENCED
) != 0) {
804 vm_page_flag_clear(m
, PG_REFERENCED
);
805 actcount
= pmap_ts_referenced(m
);
807 m
->act_count
+= (actcount
+ ACT_ADVANCE
+ 1);
812 * If the upper level VM system doesn't know anything about
813 * the page being dirty, we have to check for it again. As
814 * far as the VM code knows, any partially dirty pages are
817 * Pages marked PG_WRITEABLE may be mapped into the user
818 * address space of a process running on another cpu. A
819 * user process (without holding the MP lock) running on
820 * another cpu may be able to touch the page while we are
821 * trying to remove it. To prevent this from occuring we
822 * must call pmap_remove_all() or otherwise make the page
823 * read-only. If the race occured pmap_remove_all() is
824 * responsible for setting m->dirty.
827 vm_page_test_dirty(m
);
829 if (m
->dirty
== 0 && (m
->flags
& PG_WRITEABLE
) != 0)
838 * Invalid pages can be easily freed
840 vm_pageout_page_free(m
);
841 mycpu
->gd_cnt
.v_dfree
++;
843 } else if (m
->dirty
== 0) {
845 * Clean pages can be placed onto the cache queue.
846 * This effectively frees them.
850 } else if ((m
->flags
& PG_WINATCFLS
) == 0 && pass
== 0) {
852 * Dirty pages need to be paged out, but flushing
853 * a page is extremely expensive verses freeing
854 * a clean page. Rather then artificially limiting
855 * the number of pages we can flush, we instead give
856 * dirty pages extra priority on the inactive queue
857 * by forcing them to be cycled through the queue
858 * twice before being flushed, after which the
859 * (now clean) page will cycle through once more
860 * before being freed. This significantly extends
861 * the thrash point for a heavily loaded machine.
863 vm_page_flag_set(m
, PG_WINATCFLS
);
864 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
865 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
866 } else if (maxlaunder
> 0) {
868 * We always want to try to flush some dirty pages if
869 * we encounter them, to keep the system stable.
870 * Normally this number is small, but under extreme
871 * pressure where there are insufficient clean pages
872 * on the inactive queue, we may have to go all out.
874 int swap_pageouts_ok
;
875 struct vnode
*vp
= NULL
;
879 if ((object
->type
!= OBJT_SWAP
) && (object
->type
!= OBJT_DEFAULT
)) {
880 swap_pageouts_ok
= 1;
882 swap_pageouts_ok
= !(defer_swap_pageouts
|| disable_swap_pageouts
);
883 swap_pageouts_ok
|= (!disable_swap_pageouts
&& defer_swap_pageouts
&&
884 vm_page_count_min());
889 * We don't bother paging objects that are "dead".
890 * Those objects are in a "rundown" state.
892 if (!swap_pageouts_ok
|| (object
->flags
& OBJ_DEAD
)) {
893 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
894 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
899 * The object is already known NOT to be dead. It
900 * is possible for the vget() to block the whole
901 * pageout daemon, but the new low-memory handling
902 * code should prevent it.
904 * The previous code skipped locked vnodes and, worse,
905 * reordered pages in the queue. This results in
906 * completely non-deterministic operation because,
907 * quite often, a vm_fault has initiated an I/O and
908 * is holding a locked vnode at just the point where
909 * the pageout daemon is woken up.
911 * We can't wait forever for the vnode lock, we might
912 * deadlock due to a vn_read() getting stuck in
913 * vm_wait while holding this vnode. We skip the
914 * vnode if we can't get it in a reasonable amount
918 if (object
->type
== OBJT_VNODE
) {
921 if (vget(vp
, LK_EXCLUSIVE
|LK_NOOBJ
|LK_TIMELOCK
)) {
923 if (object
->flags
& OBJ_MIGHTBEDIRTY
)
929 * The page might have been moved to another
930 * queue during potential blocking in vget()
931 * above. The page might have been freed and
932 * reused for another vnode. The object might
933 * have been reused for another vnode.
935 if (m
->queue
!= PQ_INACTIVE
||
936 m
->object
!= object
||
937 object
->handle
!= vp
) {
938 if (object
->flags
& OBJ_MIGHTBEDIRTY
)
945 * The page may have been busied during the
946 * blocking in vput(); We don't move the
947 * page back onto the end of the queue so that
948 * statistics are more correct if we don't.
950 if (m
->busy
|| (m
->flags
& PG_BUSY
)) {
956 * If the page has become held it might
957 * be undergoing I/O, so skip it
960 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
961 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, pageq
);
962 if (object
->flags
& OBJ_MIGHTBEDIRTY
)
970 * If a page is dirty, then it is either being washed
971 * (but not yet cleaned) or it is still in the
972 * laundry. If it is still in the laundry, then we
973 * start the cleaning operation.
975 * This operation may cluster, invalidating the 'next'
976 * pointer. To prevent an inordinate number of
977 * restarts we use our marker to remember our place.
979 * decrement page_shortage on success to account for
980 * the (future) cleaned page. Otherwise we could wind
981 * up laundering or cleaning too many pages.
983 TAILQ_INSERT_AFTER(&vm_page_queues
[PQ_INACTIVE
].pl
, m
, &marker
, pageq
);
984 if (vm_pageout_clean(m
) != 0) {
988 next
= TAILQ_NEXT(&marker
, pageq
);
989 TAILQ_REMOVE(&vm_page_queues
[PQ_INACTIVE
].pl
, &marker
, pageq
);
996 * Compute the number of pages we want to try to move from the
997 * active queue to the inactive queue.
999 page_shortage
= vm_paging_target() +
1000 vmstats
.v_inactive_target
- vmstats
.v_inactive_count
;
1001 page_shortage
+= addl_page_shortage
;
1004 * Scan the active queue for things we can deactivate. We nominally
1005 * track the per-page activity counter and use it to locate
1006 * deactivation candidates.
1008 * NOTE: we are still in a critical section.
1010 pcount
= vmstats
.v_active_count
;
1011 m
= TAILQ_FIRST(&vm_page_queues
[PQ_ACTIVE
].pl
);
1013 while ((m
!= NULL
) && (pcount
-- > 0) && (page_shortage
> 0)) {
1015 * Give interrupts a chance.
1021 * If the page was ripped out from under us, just stop.
1023 if (m
->queue
!= PQ_ACTIVE
)
1025 next
= TAILQ_NEXT(m
, pageq
);
1028 * Don't deactivate pages that are busy.
1030 if ((m
->busy
!= 0) ||
1031 (m
->flags
& PG_BUSY
) ||
1032 (m
->hold_count
!= 0)) {
1033 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1034 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1040 * The count for pagedaemon pages is done after checking the
1041 * page for eligibility...
1043 mycpu
->gd_cnt
.v_pdpages
++;
1046 * Check to see "how much" the page has been used.
1049 if (m
->object
->ref_count
!= 0) {
1050 if (m
->flags
& PG_REFERENCED
) {
1053 actcount
+= pmap_ts_referenced(m
);
1055 m
->act_count
+= ACT_ADVANCE
+ actcount
;
1056 if (m
->act_count
> ACT_MAX
)
1057 m
->act_count
= ACT_MAX
;
1062 * Since we have "tested" this bit, we need to clear it now.
1064 vm_page_flag_clear(m
, PG_REFERENCED
);
1067 * Only if an object is currently being used, do we use the
1068 * page activation count stats.
1070 if (actcount
&& (m
->object
->ref_count
!= 0)) {
1071 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1072 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1074 m
->act_count
-= min(m
->act_count
, ACT_DECLINE
);
1075 if (vm_pageout_algorithm
||
1076 m
->object
->ref_count
== 0 ||
1077 m
->act_count
< pass
) {
1079 if (m
->object
->ref_count
== 0) {
1080 vm_page_protect(m
, VM_PROT_NONE
);
1084 vm_page_deactivate(m
);
1086 vm_page_deactivate(m
);
1089 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1090 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1097 * We try to maintain some *really* free pages, this allows interrupt
1098 * code to be guaranteed space. Since both cache and free queues
1099 * are considered basically 'free', moving pages from cache to free
1100 * does not effect other calculations.
1102 * NOTE: we are still in a critical section.
1105 while (vmstats
.v_free_count
< vmstats
.v_free_reserved
) {
1106 static int cache_rover
= 0;
1107 m
= vm_page_list_find(PQ_CACHE
, cache_rover
, FALSE
);
1110 if ((m
->flags
& (PG_BUSY
|PG_UNMANAGED
)) ||
1115 printf("Warning: busy page %p found in cache\n", m
);
1117 vm_page_deactivate(m
);
1120 cache_rover
= (cache_rover
+ PQ_PRIME2
) & PQ_L2_MASK
;
1121 vm_pageout_page_free(m
);
1122 mycpu
->gd_cnt
.v_dfree
++;
1127 #if !defined(NO_SWAPPING)
1129 * Idle process swapout -- run once per second.
1131 if (vm_swap_idle_enabled
) {
1133 if (time_second
!= lsec
) {
1134 vm_pageout_req_swapout
|= VM_SWAP_IDLE
;
1142 * If we didn't get enough free pages, and we have skipped a vnode
1143 * in a writeable object, wakeup the sync daemon. And kick swapout
1144 * if we did not get enough free pages.
1146 if (vm_paging_target() > 0) {
1147 if (vnodes_skipped
&& vm_page_count_min())
1149 #if !defined(NO_SWAPPING)
1150 if (vm_swap_enabled
&& vm_page_count_target()) {
1152 vm_pageout_req_swapout
|= VM_SWAP_NORMAL
;
1158 * If we are out of swap and were not able to reach our paging
1159 * target, kill the largest process.
1161 if ((vm_swap_size
< 64 && vm_page_count_min()) ||
1162 (swap_pager_full
&& vm_paging_target() > 0)) {
1164 if ((vm_swap_size
< 64 || swap_pager_full
) && vm_page_count_min()) {
1166 info
.bigproc
= NULL
;
1168 allproc_scan(vm_pageout_scan_callback
, &info
);
1169 if (info
.bigproc
!= NULL
) {
1170 killproc(info
.bigproc
, "out of swap space");
1171 info
.bigproc
->p_nice
= PRIO_MIN
;
1172 info
.bigproc
->p_usched
->resetpriority(&info
.bigproc
->p_lwp
);
1173 wakeup(&vmstats
.v_free_count
);
1174 PRELE(info
.bigproc
);
1180 vm_pageout_scan_callback(struct proc
*p
, void *data
)
1182 struct vm_pageout_scan_info
*info
= data
;
1186 * if this is a system process, skip it
1188 if ((p
->p_flag
& P_SYSTEM
) || (p
->p_pid
== 1) ||
1189 ((p
->p_pid
< 48) && (vm_swap_size
!= 0))) {
1194 * if the process is in a non-running type state,
1197 if (p
->p_stat
!= SRUN
&& p
->p_stat
!= SSLEEP
) {
1202 * get the process size
1204 size
= vmspace_resident_count(p
->p_vmspace
) +
1205 vmspace_swap_count(p
->p_vmspace
);
1208 * If the this process is bigger than the biggest one
1211 if (size
> info
->bigsize
) {
1213 PRELE(info
->bigproc
);
1216 info
->bigsize
= size
;
1222 * This routine tries to maintain the pseudo LRU active queue,
1223 * so that during long periods of time where there is no paging,
1224 * that some statistic accumulation still occurs. This code
1225 * helps the situation where paging just starts to occur.
1228 vm_pageout_page_stats(void)
1231 int pcount
,tpcount
; /* Number of pages to check */
1232 static int fullintervalcount
= 0;
1236 (vmstats
.v_inactive_target
+ vmstats
.v_cache_max
+ vmstats
.v_free_min
) -
1237 (vmstats
.v_free_count
+ vmstats
.v_inactive_count
+ vmstats
.v_cache_count
);
1239 if (page_shortage
<= 0)
1244 pcount
= vmstats
.v_active_count
;
1245 fullintervalcount
+= vm_pageout_stats_interval
;
1246 if (fullintervalcount
< vm_pageout_full_stats_interval
) {
1247 tpcount
= (vm_pageout_stats_max
* vmstats
.v_active_count
) / vmstats
.v_page_count
;
1248 if (pcount
> tpcount
)
1251 fullintervalcount
= 0;
1254 m
= TAILQ_FIRST(&vm_page_queues
[PQ_ACTIVE
].pl
);
1255 while ((m
!= NULL
) && (pcount
-- > 0)) {
1258 if (m
->queue
!= PQ_ACTIVE
) {
1262 next
= TAILQ_NEXT(m
, pageq
);
1264 * Don't deactivate pages that are busy.
1266 if ((m
->busy
!= 0) ||
1267 (m
->flags
& PG_BUSY
) ||
1268 (m
->hold_count
!= 0)) {
1269 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1270 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1276 if (m
->flags
& PG_REFERENCED
) {
1277 vm_page_flag_clear(m
, PG_REFERENCED
);
1281 actcount
+= pmap_ts_referenced(m
);
1283 m
->act_count
+= ACT_ADVANCE
+ actcount
;
1284 if (m
->act_count
> ACT_MAX
)
1285 m
->act_count
= ACT_MAX
;
1286 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1287 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1289 if (m
->act_count
== 0) {
1291 * We turn off page access, so that we have
1292 * more accurate RSS stats. We don't do this
1293 * in the normal page deactivation when the
1294 * system is loaded VM wise, because the
1295 * cost of the large number of page protect
1296 * operations would be higher than the value
1297 * of doing the operation.
1299 vm_page_protect(m
, VM_PROT_NONE
);
1300 vm_page_deactivate(m
);
1302 m
->act_count
-= min(m
->act_count
, ACT_DECLINE
);
1303 TAILQ_REMOVE(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1304 TAILQ_INSERT_TAIL(&vm_page_queues
[PQ_ACTIVE
].pl
, m
, pageq
);
1314 vm_pageout_free_page_calc(vm_size_t count
)
1316 if (count
< vmstats
.v_page_count
)
1319 * free_reserved needs to include enough for the largest swap pager
1320 * structures plus enough for any pv_entry structs when paging.
1322 if (vmstats
.v_page_count
> 1024)
1323 vmstats
.v_free_min
= 4 + (vmstats
.v_page_count
- 1024) / 200;
1325 vmstats
.v_free_min
= 4;
1326 vmstats
.v_pageout_free_min
= (2*MAXBSIZE
)/PAGE_SIZE
+
1327 vmstats
.v_interrupt_free_min
;
1328 vmstats
.v_free_reserved
= vm_pageout_page_count
+
1329 vmstats
.v_pageout_free_min
+ (count
/ 768) + PQ_L2_SIZE
;
1330 vmstats
.v_free_severe
= vmstats
.v_free_min
/ 2;
1331 vmstats
.v_free_min
+= vmstats
.v_free_reserved
;
1332 vmstats
.v_free_severe
+= vmstats
.v_free_reserved
;
1338 * vm_pageout is the high level pageout daemon.
1346 * Initialize some paging parameters.
1349 vmstats
.v_interrupt_free_min
= 2;
1350 if (vmstats
.v_page_count
< 2000)
1351 vm_pageout_page_count
= 8;
1353 vm_pageout_free_page_calc(vmstats
.v_page_count
);
1355 * v_free_target and v_cache_min control pageout hysteresis. Note
1356 * that these are more a measure of the VM cache queue hysteresis
1357 * then the VM free queue. Specifically, v_free_target is the
1358 * high water mark (free+cache pages).
1360 * v_free_reserved + v_cache_min (mostly means v_cache_min) is the
1361 * low water mark, while v_free_min is the stop. v_cache_min must
1362 * be big enough to handle memory needs while the pageout daemon
1363 * is signalled and run to free more pages.
1365 if (vmstats
.v_free_count
> 6144)
1366 vmstats
.v_free_target
= 4 * vmstats
.v_free_min
+ vmstats
.v_free_reserved
;
1368 vmstats
.v_free_target
= 2 * vmstats
.v_free_min
+ vmstats
.v_free_reserved
;
1370 if (vmstats
.v_free_count
> 2048) {
1371 vmstats
.v_cache_min
= vmstats
.v_free_target
;
1372 vmstats
.v_cache_max
= 2 * vmstats
.v_cache_min
;
1373 vmstats
.v_inactive_target
= (3 * vmstats
.v_free_target
) / 2;
1375 vmstats
.v_cache_min
= 0;
1376 vmstats
.v_cache_max
= 0;
1377 vmstats
.v_inactive_target
= vmstats
.v_free_count
/ 4;
1379 if (vmstats
.v_inactive_target
> vmstats
.v_free_count
/ 3)
1380 vmstats
.v_inactive_target
= vmstats
.v_free_count
/ 3;
1382 /* XXX does not really belong here */
1383 if (vm_page_max_wired
== 0)
1384 vm_page_max_wired
= vmstats
.v_free_count
/ 3;
1386 if (vm_pageout_stats_max
== 0)
1387 vm_pageout_stats_max
= vmstats
.v_free_target
;
1390 * Set interval in seconds for stats scan.
1392 if (vm_pageout_stats_interval
== 0)
1393 vm_pageout_stats_interval
= 5;
1394 if (vm_pageout_full_stats_interval
== 0)
1395 vm_pageout_full_stats_interval
= vm_pageout_stats_interval
* 4;
1399 * Set maximum free per pass
1401 if (vm_pageout_stats_free_max
== 0)
1402 vm_pageout_stats_free_max
= 5;
1404 swap_pager_swap_init();
1407 * The pageout daemon is never done, so loop forever.
1413 * If we have enough free memory, wakeup waiters. Do
1414 * not clear vm_pages_needed until we reach our target,
1415 * otherwise we may be woken up over and over again and
1416 * waste a lot of cpu.
1419 if (vm_pages_needed
&& !vm_page_count_min()) {
1420 if (vm_paging_needed() <= 0)
1421 vm_pages_needed
= 0;
1422 wakeup(&vmstats
.v_free_count
);
1424 if (vm_pages_needed
) {
1426 * Still not done, take a second pass without waiting
1427 * (unlimited dirty cleaning), otherwise sleep a bit
1432 tsleep(&vm_pages_needed
, 0, "psleep", hz
/2);
1435 * Good enough, sleep & handle stats. Prime the pass
1442 error
= tsleep(&vm_pages_needed
,
1443 0, "psleep", vm_pageout_stats_interval
* hz
);
1444 if (error
&& !vm_pages_needed
) {
1447 vm_pageout_page_stats();
1452 if (vm_pages_needed
)
1453 mycpu
->gd_cnt
.v_pdwakeups
++;
1455 vm_pageout_scan(pass
);
1456 vm_pageout_deficit
= 0;
1461 pagedaemon_wakeup(void)
1463 if (!vm_pages_needed
&& curthread
!= pagethread
) {
1465 wakeup(&vm_pages_needed
);
1469 #if !defined(NO_SWAPPING)
1471 vm_req_vmdaemon(void)
1473 static int lastrun
= 0;
1475 if ((ticks
> (lastrun
+ hz
)) || (ticks
< lastrun
)) {
1476 wakeup(&vm_daemon_needed
);
1481 static int vm_daemon_callback(struct proc
*p
, void *data __unused
);
1487 tsleep(&vm_daemon_needed
, 0, "psleep", 0);
1488 if (vm_pageout_req_swapout
) {
1489 swapout_procs(vm_pageout_req_swapout
);
1490 vm_pageout_req_swapout
= 0;
1493 * scan the processes for exceeding their rlimits or if
1494 * process is swapped out -- deactivate pages
1496 allproc_scan(vm_daemon_callback
, NULL
);
1501 vm_daemon_callback(struct proc
*p
, void *data __unused
)
1503 vm_pindex_t limit
, size
;
1506 * if this is a system process or if we have already
1507 * looked at this process, skip it.
1509 if (p
->p_flag
& (P_SYSTEM
| P_WEXIT
))
1513 * if the process is in a non-running type state,
1516 if (p
->p_stat
!= SRUN
&& p
->p_stat
!= SSLEEP
)
1522 limit
= OFF_TO_IDX(qmin(p
->p_rlimit
[RLIMIT_RSS
].rlim_cur
,
1523 p
->p_rlimit
[RLIMIT_RSS
].rlim_max
));
1526 * let processes that are swapped out really be
1527 * swapped out. Set the limit to nothing to get as
1528 * many pages out to swap as possible.
1530 if (p
->p_flag
& P_SWAPPEDOUT
)
1533 size
= vmspace_resident_count(p
->p_vmspace
);
1534 if (limit
>= 0 && size
>= limit
) {
1535 vm_pageout_map_deactivate_pages(
1536 &p
->p_vmspace
->vm_map
, limit
);